Washington — Teachers across America in this back-to-school season are trying to fire up students about the glories of education. With learning you can be anything you want to be, they’ll say. An inventor. A CEO. Even president of the United States.

Of course that old exhortation is true. But we have an extra-credit question. As far as Decoder can tell, only one career schoolteacher has been elected to the White House. Who was it?

Yes, we’re making some arbitrary distinctions here. By “schoolteacher,” we mean someone who’s tried to hammer some learning into kids younger than 18. That leaves out Barack Obama and Bill Clinton, both law school lecturers; Woodrow Wilson, who was Princeton’s president; and William Taft, who was a law school dean.

We’re cutting out those who taught and then quickly moved to other professions before entering public service. Wave goodbye to James Garfield and Chester Arthur, both of whom ran academies before they became lawyers.

And we’re being generous about the definition of “career.” It was brief. But it made a powerful impression on both the president in question and his students.

Give up? It was Lyndon Baines Johnson. LBJ taught fifth, sixth, and seventh grades in a predominantly Hispanic public school in the Texas town of Cotulla in 1928 and 1929. Then he taught public speaking at Sam Houston High School in Houston in 1930 and 1931. He went straight from there to Washington and a job as a congressional aide. Look at a list of the occupations of US presidents, and you’ll see that only LBJ has this line: “teacher – public official.”

And he was a good teacher. Say what you will about his presidency – there’s a lot to criticize. But at Sam Houston he molded debaters into champions. At Cotulla, a school so poor there was no lunch hour because the students had no lunches, he formed sports teams, arranged spelling bees, and drilled his charges in their subjects.